Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 311036
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
636 AM EDT SUN AUG 31 2014

.SYNOPSIS...
A BERMUDA HIGH WILL DEVELOP AND LINGER THROUGH EARLY IN THE WEEK...
RESULTING IN TYPICAL SUMMERTIME HEAT AND ISOLATED TO SCATTERED
AFTERNOON THUNDERSTORMS EACH DAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 630 AM EDT SUNDAY...LINE OF SHOWERS CONTINUES TO PUSH EAST
ACROSS THE UPSTATE AND PORTIONS OF WESTERN NC.  RECENT RADAR TRENDS
HAVE FAVORED EARLIER FORECAST AS OVERALL COVERAGE AND INTENSITY IS
DECREASING.  LIGHT FOG SPREAD ACROSS PORTIONS OF THE AREA WILL
REMAIN FOR ANOTHER HOUR OR SO BEFORE MIXING AND HEATING COMBINE TO
PROMOTE EROSION.  AS FOR THE FORECAST...MADE SLIGHT ADJUSTMENTS TO
POPS IN THE EXTREME NEAR TERM TO REFLECT LATEST RADAR TRENDS WHICH
LED TO FURTHER POP INCREASES ALONG THE I77 CORRIDOR WHILE LOWERING
POPS TO THE WEST.  ALSO TWEAKED TEMPERATURES AND DEWPOINTS TO
REFLECT LATEST OBSERVATIONS.

PREVIOUS DISCUSSION...

AS OF 325 AM EDT SUNDAY...UPPER LEVEL TROF TO THE WEST WILL CONTINUE
TO DOMINATE THE PATTERN THROUGH THE NEAR TERM FORECAST PERIOD.
LIKEWISE...ELONGATING UPPER RIDGE AND SURFACE HIGH PRESSURE OFF THE
MID ATLANTIC COAST WILL CONTRIBUTE TO INCREASING SOUTHERLY FLOW.
UPPER TROF ENERGY REMAINS THE DOMINANT FORCING MECHANISM THIS
MORNING AS BAND OF CONVECTION CONTINUES TO PUSH EAST OUT OF
NORTHEAST GA INTO WESTERN NC AND THE UPSTATE.  DESPITE LIMITED
INSTABILITY PRESENT ACROSS THE REGION...UPPER ENERGY AND SURFACE
MOISTURE ADVECTION HAVE LED TO MODERATELY DEEP UPDRAFTS SUPPORTIVE
OF PRONOUNCED RAIN RATES.  OBSERVATIONS FROM AROUND THE REGION HAVE
INDICATED THAT SOME OF THE HEAVIER CELLS ARE YIELDING APPROXIMATELY
ONE INCH PER HOUR RATES.  THAT SAID...FORWARD PROPAGATION COMBINED
WITH ANTECEDENT DRY CONDITIONS WILL INHIBIT ANY FLOODING THREATS
THIS MORNING.  LATEST MODEL GUIDANCE SOLUTIONS TO INCLUDE CAMS
INDICATE THAT THIS BAND OF CONVECTION WILL WEAKEN TOWARDS DAYBREAK
AS IT PUSHES UP INTERSTATE 85 TOWARDS THE NC PIEDMONT.  THEREFORE
THE FORECAST FEATURES NUMEROUS SHOWERS/THUNDERSTORMS ACROSS THE NC
FOOTHILLS SOUTHWARD INTO THE UPSTATE WITH ISOLATED SHOWERS POSSIBLE
AFTER DAYBREAK ACROSS THE EAST.  ALTHOUGH TEMPERATURES WILL BE SLOW
TO COOL BENEATH CLOUDY SKIES...EXPECTING INCREASED BOUNDARY LAYER
MOISTURE FROM CONVECTION TO AID IN PATCHY FOG ACROSS THE REGION.
FORTUNATELY 5-10MPH WINDS WILL LIKELY INHIBIT DEVELOPMENT OF
WIDESPREAD/DENSE FOG.

CONDITIONS WILL IMPROVE ACROSS THE REGION BY LATE MORNING WITH LOW
LEVEL STRATUS LINGERING LEADING TO MOSTLY CLOUDY SKIES.  THIS SKY
COVER IS EXPECTED TO SCATTER OUT WITH MIXING AS THE ATMOSPHERE
BEGINS TO HEAT.  MEANWHILE...ANOTHER UPPER SHORT WAVE WILL APPROACH
FROM THE WEST PROVIDING NEEDED SUPPORT FOR CONVECTION DURING THE
AFTERNOON HOURS.  UPPER LEVEL AND SURFACE RIDGE WILL REMAIN NEARLY
STATIONARY ACROSS THE SOUTHEAST WITH THE MAJORITY OF THE FORECAST
AREA RESIDING ON THE PERIPHERY.  AS A RESULT...FORECAST SOUNDINGS
ARE MODERATELY UNSTABLE WITH WEAK LOW/MID LEVEL INHIBITION WORKING
TO LIMIT CONVECTION.  EXPECTING ABOVE MENTIONED UPPER WAVE ENERGY
SLIDING EAST TO AID CONVECTION...ESPECIALLY ACROSS THE HIGH TERRAIN
WHERE CAPPING WILL BE WEAKEST.  THEREFORE POPS WILL INCREASE TO
SLIGHT CHANCE LEVELS ALONG THE INTERSTATE 85 CORRIDOR WITH SOLID
CHANCE LEVEL POPS FURTHER WEST ALONG THE MOUNTAINS.  POPS WILL TAPER
DOWN INTO THE EVENING HOURS AS THE UPPER TROF AND ASSOCIATED ENERGY
EJECT TO THE NORTHEAST AND DIURNAL COOLING COMMENCES.  IN GENERAL
TEMPERATURES THROUGH THE PERIOD WILL REMAIN AT OR JUST ABOVE NORMAL
LEVELS WITH SOME DEVIATION POSSIBLE DEPENDING ON LONGEVITY AND
COVERAGE OF CONVECTION/CLOUDS.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 205 AM SUNDAY...UPPER SUBTROPICAL ANTICYCLONE WILL REMAIN OVER
THE SERN CONUS THRU THE PERIOD WHILE A LOW AMPLITUDE UPPER TROF
MOVES EAST IN THE WRLY FLOW ACROSS THE NRN CONUS. AT THE SFC...A
BERMUDA HIGH REMAINS OVER THE SERN CONUS KEEPING TYPICAL SUMMERTIME
PATTERN ACROSS THE AREA MONDAY AND TUE. A WARM HUMID AIR MASS WITH A
LEE TROF REMAINS IN PLACE THRU THE PERIOD HELPING PRODUCE A TYPICAL
PATTERN OF DIURNAL CONVECTION WITH SCATTERED COVERAGE OVER THE MTNS
AND ISOLATED COVERAGE ELSEHWERE. A FLY IN THE OINTMENT TO THIS
SCENARIO IS A WEAK COLD FRONT THAT DROPS TOWARD THE AREA TUE NITE
AHEAD OF THE AFORE MENTIONED UPPER TROF. THIS COULD KEEP CONVECTION
GOING THRU THE NITE...ESPECIALLY ACROSS THE NC MTNS. HIGHS WILL
REMAIN NEARLY STEADY ABOVE NORMAL EACH DAY...WHILE ABOVE NORMAL LOWS
MON NITE RISE A COUPLE OF DEGREES TUE NITE.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 335 AM SUNDAY...GUIDANCE IN GOOD AGREEMENT THRU THU. THE UPPER
ANTICYCLONE REASSERTS ITSELF ACROSS THE SERN CONUS AS AN UPPER TROF
MOVES EAST OF THE AREA. SOME WEAK SHORT WAVE ENERGY IS STILL ABLE TO
MOVE ACROSS THE AREA THRU THE RIDGING. AT THE SFC...A WEAK COLD
FRONT DRIVEN BY THE DEPARTING TROF MOVES INTO THE AREA AND STALLS.
EVEN THO THE FRONT WASHES OUT...A LOW LEVEL CONVERGENCE BOUNDARY
REMAINS IN PLACE. THIS LEADS TO SCT MAINLY DIURNAL CONVECTION WED
AND THU. THE LATEST GFS SHOWS THE RIDGE RETROGRADING ALLOWING SHORT
WAVES TO DROP ACROSS THE AREA FRI AND SAT IN THE DEVELOPING WEAK
NWLY FLOW. THE ECMWF KEEPS THE RIDGE IN PLACE FRI...THEN WEAKENS IT
AND SUPPRESSES IT TOWARD THE GULF COAST SAT. HOWEVER...THE RIDGE IS
STILL STRONG ENUF TO KEEP ANY SHORT WAVES AND WLY FLOW NORTH OF THE
AREA. EVEN WITH THE UPPER AIR DIFFERENCES...THE SFC FEATURES ARE
REMARKABLY SIMILAR. THE WEAK SFC BOUNDARY HOLDS ON FOR ONE MORE DAY
FRI LEADING TO ANOTHER ROUND OF MAINLY DIURNAL SCT CONVECTION. THE
GFS THEN BRINGS A COLD FRONT INTO THE AREA SAT WHILE THE ECMWF
BRINGS IT TOWARD...BUT NOT QUITE INTO THE CWFA. GIVEN THE
DIFFERENCES...HAVE KEPT PRECIP AS SCT MAINLY DIURNAL CONVECTION.
ABOVE NORMAL HIGHS WED DROP TO NEAR NORMAL FOR FRI AND SAT...WHILE
LOWS BOUNCE AROUND ABOVE NORMAL THRU THE PERIOD.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
AT KCLT...VFR CONDITIONS WILL PREVAIL FOR THE MAJORITY OF THE TAF
CYCLE WITH THE EXCEPTION OF MVFR LEVEL VSBY DUE TO INITIAL SHRA
ACTIVITY.  INITIALIZED TAF VFR WITH A 1HR TEMPO TO ACCOUNT FOR ABOVE
MENTIONED SHRA INDUCED MVFR VISB.  BY 13Z CONDITIONS WILL IMPROVE
UNDER BKN/OVC LOW LEVEL STRATUS LASTING THROUGH MUCH OF THE MORNING
BEFORE LOW LEVEL MOISTURE MIXES OUT.  SKIES WILL FEATURE BKN
MID/HIGH LEVEL CLOUDS WITH INCREASING SOUTHERLY WINDS BY MIDDAY
LASTING THROUGH THE PERIOD.  REMOVED PREVIOUS PROB30 FOR AFTERNOON
TSRA AS LATEST SOUNDINGS INDICATE CAP WILL MOST LIKELY HOLD.

ELSEWHERE...A MIXTURE OF VFR/MVFR/IFR CONDITIONS WILL HIGHLIGHT THIS
TAF CYCLE AT ALL SITES.  ABOVE MENTIONED BAND OF CONVECTION WILL
CONTINUE PUSHING EAST AND AWAY FROM THE SC SITES AND KAVL.
HOWEVER...EXPECTING MVFR/IFR VISB AND OR CIGS TO PERSIST FOR AN HOUR
OR SO BEHIND THE DEPARTING LINE.  INITIALIZED ONLY KHKY WITH WX
MENTION AS LINE OF SHRA WILL PERSIST FOR A FEW MORE HOURS.
CONDITIONS WILL SLOWLY IMPROVE BY MID/LATE MORNING AT ALL SITES AS
ABOVE MENTIONED SHRA ERODES ALONG WITH INCREASING CLOUD BASES.  VFR
WILL PREVAIL LATE IN THE PERIOD WITH THE EXCEPTION OF PROB30 MENTION
AT KAVL AND KHKY TO ACCOUNT FOR AFTERNOON CONVECTION.  WINDS THROUGH
THE PERIOD WILL REMAIN SOUTHERLY WITH FLOW INCREASING INTO SUNDAY
AFTERNOON.

OUTLOOK...GENERALLY VFR CONDITIONS ARE EXPECTED THROUGH EARLY NEXT
WEEK WITH THE EXCEPTION FOR RESTRICTIONS IN THE EARLY MORNING DUE TO
LOW CLOUDS AND FOG...PRIMARILY IN THE MOUNTAIN VALLEYS. DIURNAL
CONVECTION IS EXPECTED EACH AFTERNOON WITH THE MOST COVERAGE OVER
THE MOUNTAINS.

CONFIDENCE TABLE...

            10-16Z        16-22Z        22-04Z        04-10Z
KCLT       HIGH  97%     HIGH 100%     HIGH 100%     MED   62%
KGSP       LOW   59%     HIGH  94%     HIGH 100%     MED   62%
KAVL       HIGH  83%     HIGH 100%     HIGH 100%     MED   73%
KHKY       HIGH  90%     HIGH 100%     HIGH 100%     MED   62%
KGMU       LOW   53%     HIGH  94%     HIGH 100%     MED   62%
KAND       MED   63%     HIGH  92%     HIGH 100%     MED   62%

THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULED TAF ISSUANCE FLIGHT RULE CATEGORY. COMPLETE
HOURLY EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE
FORECASTS ARE AVAILABLE AT THE FOLLOWING LINK: (MUST BE LOWER CASE)

WWW.WEATHER.GOV/GSP/AVIATION_TABLES

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...RWH
NEAR TERM...CDG
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...CDG





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